According to a first aspect of the present invention there is provided a method of detecting faults within a telecommunications network, said telecommunications network comprising a plurality of entities. The method comprises grouping said entities into one or more groups based on the call traffic handled by said entities or on the call traffic said entities are configured to handle, for at least one of said groups, monitoring the call length pattern of a plurality of grouped entities of said group, and for at least one of said grouped entities, comparing the monitored call length pattern of the grouped entity with the monitored call length pattern of one or more of the other grouped entities to determine if the behavior of said grouped entity is indicative of a fault. The entities may comprise nodes of the network or hardware elements within one or more nodes of the network.